[leetcode] Hash Table-760. Find Anagram Mappings

Posted 2020-10-20 chenhan05

Given two lists Aand B, and B is an anagram of A. B is an anagram of A means B is made by randomizing the order of the elements in A.

We want to find an index mapping P, from A to B. A mapping P[i] = j means the ith element in A appears in B at index j.

These lists A and B may contain duplicates. If there are multiple answers, output any of them.

For example, given

A = [12, 28, 46, 32, 50]
B = [50, 12, 32, 46, 28]

 

We should return

[1, 4, 3, 2, 0]

as P[0] = 1 because the 0th element of A appears at B[1], and P[1] = 4 because the 1st element of A appears at B[4], and so on.

 

Note:

1. A, B have equal lengths in range [1, 100].
2. A[i], B[i] are integers in range [0, 10^5].

   class Solution {  
   public:  
       vector<int> anagramMappings(vector<int>& A, vector<int>& B) {  
           unordered_map<int, int> m;  
           vector<int> res;  
           for (int i = 0; i < B.size(); i++)  
               m[B[i]] = i;  
           for (auto& a : A) {  
               if (m.count(a)) {  
                   res.push_back(m[a]);  
               }  
               else {  
                   res.push_back(0);  
               }  
           }  
           return res;  
       }  
   };